(CNN) -- Six people, including one minor, were killed Sunday in a natural gas explosion at a resort in Playa del Carmen, Mexico, authorities and state media reported.

Another 15 or so were injured, according to the local attorney general's office, with the injured including employees of the hotel and tourists from Canada and the United States. The U.S. State Department said two of those injured were Americans.

One of the Canadian victims was a minor, Notimex, Mexico's state news agency reported.

Earlier, authorities had said that as many as 20 people could have been injured in the blast.

The explosion was likely caused by a buildup of natural gas that somehow ignited, but the official cause is under investigation, the attorney general's office said.

Police Commander Arturo Guillermo had said earlier that a gas line or stove exploded at the Grand Riviera Princess.

Video from the scene on Mexico's east coast showed debris spilled into a grassy area in front of an area covered by thatched roofs where the restaurant presumably sits.

The explosion happened around 9 a.m. Sunday morning in the lobby of the hotel. Emergency personnel responded and transferred the injured people to an area hospital for treatment.

"Right now we have personnel on site," said U.S. State Department spokeswoman Gini Staab.

The two injured Americans were taken to a hospital, she said. Authorities, including consular agents and a consular officer, were on site at the hotel assisting U.S. citizens staying there, according to Staab.